1. Field of the Invention
This invention relates to operational amplifiers and, more specifically, to an operational amplifier having selectively programmable digitally operated gain circuitry on the same chip.
2. Brief Description of the Prior Art
Programmable operational amplifiers in accordance with the prior art have typically been programmed with resistor selection that requires a physical change to the circuitry involved, the resistors being disposed external to the chip containing the amplifier circuitry. In such prior art programmable operational amplifiers, current has been passed through a resistor that must be physically changed in the circuit to change the gain of the amplifier. The major problem with this approach is that the resistors are selected in a non-programmable manner external to the chip containing the operational amplifier. It is desired to provide the same type of function on a single chip.